Strawberry growers face losses from pallidosis disease

Several Santa Barbara County, Calif. strawberry growers are dealing with pallidosis-related decline disease in some strawberry fields this summer.
Strawberry grower Jerry Cardenas of Santa Maria lost about $300,000 due to the disease by late July.
Pallidosis is a viral disease which requires several viruses to combine to cause the disease.

Cardenas’ farm is located in the heart of the Santa Maria Valley, about seven miles east of the Central Coast.

Cardenas is one of about 400 strawberry growers in California. Combined, these growers earned about $2 billion in farm income in 2011 from about 38,000 acres of berries.

About a dozen of Cardenas’ 90 acres of strawberries were severely infected with the disease. Of the two strawberry varieties grown, the most damage was in the San Andreas variety. The BG-1975 variety had less damage.

No chemical product can prevent or control the disease; not even fungicides or soil fumigation.

PCA input

For Cardenas, plant discoloration started around May 1 as the plant turned from a normal green color to a purple shade. Plants were dead by late May and into early June. Cardenas immediately contacted pest control advisor (PCA) John Gracia of AG RX in Santa Maria.

After plant examination, Gracia first thought mites could be the culprit. Yet in March, the miticides Epi-Mek and Acramite were applied to the crop. Due to a heavier than normal whitefly population this spring, Gracia had prescribed the insecticides Courier, Esteem, and Oberon which provided good whitefly control.

“The disease was most likely brought in by the whitefly,” Gracia said.

The whitefly is generally not a major concern in strawberry production in the valley. Yet an increase of strawberry acreage likely increased whitefly numbers.

“In the future, we have to be more aggressive on whitefly control,” Gracia said. “We cannot afford to take the risk anymore.”

Given the situation, Gracia says area-wide grower control of whiteflies is needed to protect the crop.

“If one strawberry grower keeps their field clean but their neighbor doesn’t then none of the fields will stay clean,” Gracia said.

He says additional research is needed on the disease and related viruses.

Gomez crop damage

A few miles north of Guadalupe in San Luis Obispo County, Viridiana Gomez stood by her pick-up parked next to a 13-acre field of San Andreas strawberries grown by the Gomez family.

Viridiana’s father, Juan Gomez, is president of Del Campo Berry Farms, based in Santa Maria.

This is the Gomez family’s first crop of strawberries. The transplants were planted last October. The Gomez’s first noticed the plants changing colors in March. Two to three weeks later some plants were dying.

“When we first saw a problem, we didn’t have a clue on the cause,” Viridiana said. “We thought it might be a soil problem or a chemical issue.”

The Gomez’s PCA took a sample which was submitted to a lab for analysis. The sample came back positive for pallidosis.

About two-thirds of the Gomez crop has been lost to pallidosis. The strawberry crop was grown for the juice market. Dead plants were removed. New transplants were planted.

“The field looks like its getting better now,” Gomez said.

Strawberries are nearly a $2 billion crop in California.

Pallidosis management

The greenhouse whitefly is a one-millimeter-long insect with four nymphal instars which are flat, oval, and transparent. Fifth instar nymphs move around as crawlers searching for a preferred feeding site on the leaf.

Laboratory analysis is critical to determine if the plant malady is present. Growers can provide samples to UCCE or county agricultural commissioner’s office for no-charge testing. Samples can also be sent to commercial labs.

California strawberry growers produce almost 90 percent of the nation’s crop, according to the California Department of Food and Agriculture. Strawberries are the state’s 14thlargest exported crop with export values of about $336 million.

The leading strawberry counties include Monterey, Ventura, Santa Barbara, Santa Cruz, and San Luis Obispo, respectively.